Wind turbine blade with reinforcement for preventing delamination

Abstract

The present invention relates to a reinforced blade for a wind turbine, in particular the adhesive joint line is reinforced to better withstand forces leading to blade failure due to peeling effects in the joint line. The blade has at least one elongated reinforcing member connected within the blade shell for increasing the strength of the adhesive joint line of the blade. Each of the at least one elongated reinforcing member has a first end and a second end and extends in a longitudinal direction between the first end and the second end, and wherein the first end is connected to the blade shell and the second end is connected to a support or flatback, thereby reducing peeling stresses in the adhesive joint line.

Description

Technical Field

[0001] The present invention relates to a reinforced blade for a wind turbine, and more particularly to a blade having an elongated reinforcing member in the blade to prevent or reduce deformation and peeling stress in the connecting line section. Background Technology

[0002] Typically, wind turbine blades have an aerodynamic blade shell shape and at least one support, such as a transverse support or truss. The support can be a single support, but two supports are commonly used. The two supports, along with a portion of the blade shell extending between them, together form what is known as a box profile. The top and bottom of the box profile are often referred to as a shroud or truss shroud. Some types of blades are designed with trusses in the form of box profiles, which are manufactured separately and connected between prefabricated surface blade shells. The aerodynamic shell is typically made of laminates of fiber-reinforced plastics, fiberglass, and / or other materials. Typically, the aerodynamic shell is made of two blade shell sections assembled by adhesive connecting lines to form the blade shell.

[0003] Under normal operating conditions, wind turbine blades experience loads angular to the flap-wise direction. This load is typically decomposed into a component in the flap-wise direction and a component in the edge-wise direction. The flap-wise direction is approximately perpendicular to the transverse axis passing through the blade cross-section. Therefore, the flap-wise direction can be interpreted as the direction in which aerodynamic lift acts on the blade, or the opposite / reverse direction. Edge-wise loads occur approximately perpendicular to the flap-wise direction. Blades also experience torsional loads, primarily aerodynamic, gravitational, and inertial loads. These loads can cause the blades to undergo resonant motion or oscillations approximately at their torsional natural frequency.

[0004] When the blade is subjected to a teetering load combining flapping and torsional loads, the cross-sectional deformation of the blade is shown in the figure. Figure 1 This shear-torsional deformation of the cross-section induces peel stress in the bonded joint profile, which can lead to fatigue failure in the bonded joint (also known as the bonded joint profile) at the trailing edge (generally where the trailing edge is shaped as a flat-back airfoil, where the two shell parts are joined), and in the bonded joint profile between the support and the blade shell. Furthermore, deformation of the blade shell can cause deformation of both the blade shell and the support, and / or the trailing edge region, especially when the blade design includes a flat-back profile, see [reference needed]. Figure 1This cross-sectional shear distortion phenomenon may lead to fatigue failure of the adhesive bonding line between the support and the blade housing, and / or may lead to fatigue failure of the adhesive bonding line between the blade housing at the trailing edge.

[0005] Subsequently, fatigue failure of the bonded joint line in the trailing edge, and fatigue failure of the bonded joint line between the blade shell and one or more supports, can ultimately lead to blade fracture. Deformation can also cause blade shell buckling, which reduces the ultimate strength of the blade, as the blade shell typically bears the load. Furthermore, deformation impairs the aerodynamic efficiency of the blade because the designed shape of the blade profile cannot be maintained. Flapping loads combined with torsional loads can also cause the trailing edge of the blade to deform in a stable back-buckling mode. This is caused by the blade bending from the leading edge towards the trailing edge. The blade material at the leading edge is then subjected to tension, while the trailing edge is subjected to compression. Because the trailing edge may be relatively thin, it cannot withstand significant compressive forces before bending beyond the neutral plane of the trailing edge. When this occurs, some of the load on the trailing edge is transferred and distributed to a portion of the blade shell farther from the trailing edge until force equilibrium is established. Although this deformation may not lead to immediate failure, it reduces the safety margin of the blade's general failure load and increases peel and shear stresses in the trailing edge.

[0006] Therefore, there is a need for a wind turbine blade that prevents or reduces deformation of the bonded joint line portion, and that strengthens the blade structure without significantly increasing the overall weight of the blade. Another object of the present invention is to provide a wind turbine blade with increased overall strength. Summary of the Invention

[0007] Another object of the present invention is to provide a wind turbine blade with increased resistance to fatigue failure.

[0008] Another object of the present invention is to provide a wind turbine blade with increased torsional stiffness.

[0009] Another object of the present invention is to provide a wind turbine blade with increased resistance to trailing edge buckling, preferably a wind turbine blade with increased resistance to trailing edge buckling in a flat trailing edge.

[0010] Another object of the present invention is to provide a wind turbine blade with improved resistance to blade profile deformation. Yet another object of the present invention is to provide a reinforcing blade profile for a wind turbine blade.

[0011] Therefore, the object of the present invention is to provide a wind turbine blade with improved resistance to blade shell deformation.

[0012] Another object of the present invention is to provide a wind turbine blade with reduced weight and reduced cost.

[0013] Another object of the present invention is to provide a wind turbine blade with improved connection reliability between parts of the blade housing and between the blade housing and the support.

[0014] Another object of the present invention is to provide a wind turbine blade that can operate under severe aerodynamic loads and optimize aerodynamic efficiency (e.g., blade energy output).

[0015] Another object of the present invention is to provide an alternative to the prior art.

[0016] According to a first aspect of the invention, the above and other objectives are achieved by a wind turbine blade with a total length exceeding 40 meters, the wind turbine blade comprising: a blade shell having a cross-section with an aerodynamic profile; and at least one elongated reinforcing member connected within the blade shell to increase the strength of the blade, each of the at least one elongated reinforcing member having a first end and a second end and extending longitudinally between the first end and the second end, wherein the first end is connected to an upper portion or a lower portion of the blade shell, and the second end is connected to a support or a flat back. According to a second aspect of the invention, the above and other objectives are achieved by a method for increasing the strength of a wind turbine blade with a total length exceeding 40 meters, the wind turbine blade having a blade shell with a cross-section with an aerodynamic profile, the method comprising the steps of: positioning at least one elongated reinforcing member within the blade shell, each of the at least one elongated reinforcing member having a first end and a second end and extending longitudinally between the first end and the second end, connecting the first end to an upper portion or a lower portion of the blade shell, and connecting the second end to a support or a flat back. The wind turbine blade can be used in vertical axis wind turbines (such as Darrieux wind turbines, Windstar turbines, etc.), or preferably, the wind turbine blade can be used in horizontal axis wind turbines, such as common modern wind turbines, which are usually three-bladed wind turbines, and sometimes two-bladed or even single-bladed wind turbines (with counterweights).

[0017] The blade shell of a wind turbine blade may preferably, but not exclusively, comprise composite or laminated materials. This material may preferably, but not exclusively, comprise glass fiber and / or carbon fiber and / or other durable and flexible or rigid materials, which typically have a high strength-to-weight ratio. The material may also comprise at least partially lightweight metals or alloys. The blade shell may typically be a laminate and / or a sandwich structure. Preferably, at least one of at least a few elongated reinforcing members extends in a direction substantially perpendicular to the longitudinal extension of the blade. In the case of a curved blade, where the longitudinal extension of the blade forms a non-linear curve in space, the elongated reinforcing member extends in a direction substantially perpendicular to the longitudinal extension of the blade near the associated elongated reinforcing member.

[0018] The elongated reinforcing member forms an angle with the longitudinal extension of the blade near the associated elongated reinforcing member. Preferably, the angle is in the range of 70° to 110°, more preferably, the angle is in the range of 80° to 100°, and even more preferably, the angle is in the range of 85° to 95°.

[0019] At least one elongated reinforcing member may form an angle between 10 and 80 degrees with the blade's profile chord line. Preferably, at least one elongated reinforcing member may form an angle between 30 and 60 degrees with the blade's profile chord line. More preferably, at least one elongated reinforcing member may form an angle between 40 and 50 degrees with the blade's profile chord line. The blade's profile chord line is an imaginary surface that includes the blade's leading edge and trailing edge and extends between the leading and trailing edges. Therefore, the flapping direction is parallel to the profile chord line, and the flaring direction is perpendicular to the profile chord line. A wind turbine blade may include a plurality of elongated reinforcing members positioned at intervals along the longitudinal extension of the blade.

[0020] The blade according to the invention may also include one or more support members. Wind turbine blades with one or more support members are well known. Conventional support members have a longitudinal extension in the longitudinal direction of the blade and a transverse extension generally perpendicular to the profile chord of the blade. One or more conventional support members primarily reinforce the blade along its longitudinal direction. The support member may also be referred to as a web or shear web. The conventional support member or web can be constructed from any type of load-bearing elongated structural member (e.g., a transverse support or truss), for example shaped into an I-shaped or C-shaped profile, preferably made of fiber-reinforced plastic or other suitable material. Typically, the conventional support member extends approximately along the entire length of the blade.

[0021] Preferably, the elongated reinforcing member has a straight shape. If the elongated reinforcing member is not straight, its shape may be straightened when subjected to tensile forces that cause the ends of the elongated reinforcing member to move, which is obviously undesirable.

[0022] Elongated reinforcing members can be composed of any type of load-bearing elongated structural member. They may include one or more elements selected from rods, plates, and pipes, capable of resisting compressive and tensile forces. Since elongated reinforcing members do not necessarily need to resist compressive forces, they may also include one or more elements selected from wires, ropes, strands, fibers, and fabric webs. Elements can have any suitable cross-section, such as generally circular or polygonal sections, including generally rectangular, triangular, annular, oval, elliptical, etc., but annular or oval shapes are preferred.

[0023] The components can be used individually or as a group of individual components to form a “thicker” component. In particular, the components can include fibers with very high stiffness and strength, such as glass fiber, carbon fiber, aramid fiber, polyethylene fiber, PBO fiber (poly(p-phenylenebenzodioxazole) fiber), etc.

[0024] Long reinforcing members can be made from any suitable material. For rods, plates, and pipes, fiber-reinforced plastics are currently preferred. Long reinforcing members can also be made from wood such as bamboo, birch, plywood, etc.

[0025] Long reinforcing members can also be made of steel, lightweight alloys, etc.

[0026] Long reinforcing members can also be made from plant fiber-based materials (such as bast fibers, like flax and jute) with high cellulose content. These fibers can be used as reinforcements in composite materials (such as reinforced plastics) or in the form of wires or rods. Long reinforcing members can also be made from combinations of the above materials.

[0027] The elongated reinforcing member only needs to have high tensile strength; preferably, it does not necessarily need to bear other loads, allowing it to be thin and thus minimizing its weight and cost. The thickness of the elongated reinforcing member is preferably less than 10 times the maximum thickness of the blade shell, more preferably less than 5 times the maximum thickness of the blade shell, even more preferably less than 2 times the maximum thickness of the blade shell, and most preferably less than the maximum thickness of the blade shell.

[0028] The connecting portion on the inner surface of the blade profile can, in principle, be positioned anywhere on the inner surface; however, care should be taken to ensure that the chosen positioning is suitable for the elongated reinforcing member to provide a reasonable and useful reinforcement to the associated bonded connection line. The connecting portion can include any suitable type of connection, such as welding, gluing, melting, fusion, or other simple mechanical connections. The elongated reinforcing member itself may include connecting portions, or the elongated reinforcing member may include additional connecting portions or connection parts adapted to engage or mate with the inner surface of the blade housing and connecting portions on one or more supports / flat backs.

[0029] The connector can be a releasable connector, which can include any suitable type of connection, such as snap-fit, press-fit, tongue and groove connector or other simple mechanical connector.

[0030] When the aerodynamic profile is subjected to loads in the flaring, flapping, and torsional directions, the elongated reinforcing member fixes and maintains the shape of the area surrounding the bonded joint line. This significantly improves the overall strength of the aerodynamic profile because its resistance to buckling is also increased.

[0031] The elongated reinforcing member according to the invention improves the peel strength of the adhesive bonding line portion. One of the at least one elongated reinforcing member may form an angle with another elongated reinforcing member.

[0032] The angle can be in the range of 10° to 50°. Preferably, in the cross-section of the blade, at least one elongated reinforcing member extends at approximately a 45-degree angle to the chord line of the blade profile. Two or more elongated reinforcing members can be positioned in a spaced-apart relationship along at least a portion of the longitudinal extension of the blade, such that adjacent elongated reinforcing members are mounted at different angles relative to the chord line of the blade profile.

[0033] The maximum spacing between two elongated reinforcing members can be based on specific requirements, such as, but not limited to, the need for a particularly robust wind turbine blade design, for example, when the wind turbine is expected to withstand repeated severe weather conditions, such as when installed at sea or in mountainous areas.

[0034] Elongated reinforcing members may be positioned only in certain portions of the blade, without a predetermined or calculated maximum spacing. In particular, but not exclusively, elongated reinforcing members may be positioned at locations where significant deformation is expected or has already occurred in the bonded joint line. This location may be at the inner third, middle third, or outer third along the blade's length.

[0035] At least one of the elongated reinforcing members may include a composite material, such as glass fiber reinforced plastic or carbon fiber reinforced plastic or any other fiber-reinforced material.

[0036] At least one of the elongated reinforcing members may be connected, threaded, or laminated to the blade housing, support, or flat back. Attached Figure Description

[0037] The invention will be described in more detail below with reference to embodiments illustrated in the accompanying drawings. It should be emphasized that the illustrated embodiments are for illustrative purposes only and should not be used to limit the scope of the invention.

[0038] For clarity, the accompanying drawings are schematic and simplified, showing only the details necessary for understanding the invention, while other details have been omitted.

[0039] In addition to the embodiments shown, the invention may be practiced in various forms, and the invention should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure is comprehensive and complete and fully conveys the scope of the invention to those skilled in the art.

[0040] Figure 1 The image shows a cross-section through a wind turbine blade. Figure 2 A cross-section is shown through a wind turbine blade with an elongated reinforcing member according to an embodiment of the present invention. Figure 3 A cross-section is shown through a wind turbine blade with an elongated reinforcing member according to another embodiment of the invention. Figure 4 The diagram shows a cross-section through a wind turbine blade with an elongated reinforcing member according to yet another embodiment of the invention. Figure 5 The diagram shows a cross-section through a wind turbine blade according to yet another embodiment of the invention, the blade having load-bearing rectangular or box-shaped elements and elongated reinforcing members. Figure 6 A cross-section is shown through a wind turbine blade with an elongated reinforcing member according to an embodiment of the present invention, wherein the elongated reinforcing member includes a clamping structure. Figure 7 The diagram shows a cross-section through a wind turbine blade with an elongated reinforcing member according to yet another embodiment of the invention, the elongated reinforcing member including a clamping structure, and Figure 8A cross-section is shown through a wind turbine blade according to an embodiment of the present invention, the wind turbine blade having a truss cover and having an elongated reinforcing member. Detailed Implementation

[0041] Figure 1 Schematic cross-sections of a wind turbine blade are shown in an unloaded position (solid line) and a loaded position (dashed line). This cross-section illustrates a type of airfoil commonly referred to as a flat-back airfoil. Throughout this disclosure, a flat-back airfoil is defined as an airfoil with a trailing edge thickness exceeding 2% of the airfoil chord length. The term "flat-back" is used for any shape of trailing edge, regardless of whether the trailing edge is flat, round, or elliptical, and regardless of the angle of the flat-back region with one or more internal supports or airfoil chords. Clearly, Figure 1 The airfoil section shown will experience increased peel loads at any bonded joint line between any blade housing and any support member in the blade casing. It is equally evident that any bonded joint line in the flat-back region of the airfoil section will experience increased peel loads when the blade is under load (see...). Figure 1 (The dotted line in the image). The disclosure of this invention describes different methods for reinforcing these bonded joint lines by using elongated reinforcing members, which are primarily used to prevent unwanted peeling stresses in the bonded joint lines, thereby preventing bond failure of the bonded joint lines and ultimately extending the blade life.

[0042] Figure 2 A schematic cross-section of a wind turbine blade is shown, having an elongated reinforcing member between the upper portion of the blade shell and a support, an elongated reinforcing member between the lower portion of the blade shell and the support, and an elongated reinforcing member between the flat back and the lower blade shell. The elongated reinforcing member is connected to the inner surface of the blade and to the support / flat back, but the elongated reinforcing member can also be connected by any other means such as overlay, bolting, threaded connection, or even by allowing the elongated reinforcing member to penetrate the blade shell, support, and / or flat back and then combining it with a connection, overlay, bolting, or threaded connection. Figure 2 In a preferred embodiment of the invention, the elongated reinforcing member is made of a composite material skin such as glass fiber or carbon fiber, and in this preferred embodiment of the invention, it is combined with a core material to form a sandwich structure.

[0043] Figure 3 A schematic cross-section of a wind turbine blade is shown, the blade having an elongated reinforcing member between the upper portion of the blade shell and a support member, and an elongated reinforcing member between the lower portion of the blade shell and a support member. Figure 3The airfoil shown is not a flat-back type airfoil because the trailing edge thickness is less than 2% of the airfoil chord length. Therefore, the reinforcement of the trailing edge connecting line is not within the scope of the present invention. Figure 3 The elongated reinforcing member shown in this preferred embodiment of the invention is made of a solid composite material such as glass fiber reinforced plastic or carbon fiber reinforced plastic, but the elongated reinforcing member can also be made of any other material. The elongated reinforcing member is connected to the inner surface of the blade and to the support / flat back, but the elongated reinforcing member can also be connected by any other means such as overlay, bolting, threaded connection, or even by allowing the elongated reinforcing member to penetrate the blade shell, support, and / or flat back and then combining it with a connection, overlay, bolting, or threaded connection.

[0044] Figure 4 A schematic cross-section of a wind turbine blade is shown, comprising elongated reinforcing members between the upper portion of the blade shell and a support, an elongated reinforcing member between the lower portion of the blade shell and the support, and an elongated reinforcing member between the flat back and the lower blade shell. The elongated reinforcing member has a generally triangular cross-section to enhance the stiffness of the bonded joint line. The elongated reinforcing member between the blade shell and the support is positioned only on one side of the support, but it is also possible to have an elongated reinforcing member on the other side of the support, thereby further reinforcing the bonded joint line. These elongated reinforcing members are connected to the inner surface of the blade and to the support / flat back, but they can also be connected in any other manner.

[0045] Figure 5 A schematic cross-section of a wind turbine blade is shown. The blade cross-section shows a rectangular or box-shaped element bearing the load, where the support and truss cover are both manufactured as a single piece and connected to the blade casing. This internal blade structure design is common in blades from some blade manufacturers, although it is not the most frequently used design. Figure 5 Elongated reinforcing members are shown between the upper portion of the blade casing and the vertical portion (representing the support) of the load-bearing rectangular or box-shaped element, and between the lower portion of the blade casing and the same support portion of the load-bearing rectangular element. The schematic cross-section of this wind turbine blade is not a flat-back airfoil, therefore... Figure 5 There are no elongated reinforcing members in the trailing edge region. As in this preferred embodiment of the invention, Figure 5The elongated reinforcing member shown is made of a solid composite material, such as glass fiber reinforced plastic or carbon fiber reinforced plastic, but it can also be made of any other material. The elongated reinforcing member is connected to the inner surface of the blade and to the support portion of the load-bearing rectangular or box-shaped component, but it can also be connected by any other means or principle.

[0046] Figure 6 A schematic cross-section of a wind turbine blade is shown, the blade having an elongated reinforcing member between the upper portion of the blade shell and a support, an elongated reinforcing member between the lower portion of the blade shell and the support, and an elongated reinforcing member between the flat back and the lower portion of the blade shell. In the present invention... Figure 6 In the preferred embodiment shown, the elongated reinforcing member includes a clamping structure comprising a core material (such as foam or balsa wood) and a skin (such as glass fiber or carbon fiber) covering the core material. The elongated reinforcing member has a generally triangular cross-section to enhance the stiffness of the bonded joint line. The elongated reinforcing member between the blade shell and the support is positioned only on one side of the support, but it can also be present on the other side of the support, further reinforcing the bonded joint line. The elongated reinforcing member is connected to the inner surface of the blade and to the support / flat back, but it can also be connected by any other means such as over-lamination, bolting, or threading.

[0047] Figure 7 A schematic cross-section of a wind turbine blade is shown, the wind turbine blade having an elongated reinforcing member between the upper portion of the blade shell and a support member, an elongated reinforcing member between the lower portion of the blade shell and a support member, and an elongated reinforcing member between the flat back and the lower portion of the blade shell. Figure 7 The blade shown includes two truss covers with a gap between them, and a support is positioned at the truss cover as is most commonly seen in wind turbine blade structures, because the support has higher strength and stiffness than the clamping structure of the blade shell. In the present invention... Figure 7 In the preferred embodiment shown, the elongated reinforcing member includes a clamping structure comprising a core material (such as foam or balsa wood) and a skin (such as glass fiber or carbon fiber) covering the core material. The elongated reinforcing member is connected to the inner surface of the blade and to a support / flat back, but the elongated reinforcing member can also be connected by any other means such as over-lamination, bolting, or threading. Figure 7The elongated reinforcing member shown is made of fiber-reinforced plastic and core material to form a sandwich structure, but the elongated reinforcing member can also be made of any other material. The elongated reinforcing member is connected to the inner surface of the blade and to the support portion of the load-bearing rectangular unit, but the elongated reinforcing member can also be connected by any other means such as overlay, bolted connection, or threaded connection.

[0048] Figure 8 A schematic cross-section of a wind turbine blade is shown, the wind turbine blade having an elongated reinforcing member between the upper portion of the blade shell and a support member, an elongated reinforcing member between the lower portion of the blade shell and a support member, and an elongated reinforcing member between the flat back and the lower portion of the blade shell. Figure 8 The cross section of the blade shown is... Figure 2 , Figure 4 , Figure 6 and Figure 7 The same illustration shows two truss covers with a gap between them, and a support member is positioned at the truss cover because the support member has higher strength and stiffness than the clamping structure of the blade shell. In the present invention... Figure 8 In the preferred embodiment shown, the elongated reinforcing member comprises a solid composite material serving as the primary load-bearing structure. The elongated reinforcing member is threaded. Figure 8 (Not shown) to the inner surface of the blade and threaded to the support / flat back, but the elongated reinforcement can also be connected by any other means such as over-lamination or connection. Figure 8 The elongated reinforcing member shown is made of composite materials such as glass fiber or carbon fiber reinforced plastic, but the elongated reinforcing member can also be made of any other material.

[0049] Parts list 1. Support components 2. Flat back 3. Covers, truss covers 4. Elongated reinforcing member 5. Adhesive connecting lines 6. Clamping components 7. Upper part of the blade shell 8. The lower part of the blade shell.

Claims

1. A wind turbine blade with a total length exceeding 40 meters, the wind turbine blade comprising: - A blade casing having a cross-section with an aerodynamic profile, and - At least one elongated reinforcing member, said at least one elongated reinforcing member being connected within the blade housing to increase the strength of the blade. Each of the at least one elongated reinforcing member has a first end and a second end and extends longitudinally between the first end and the second end, wherein the first end is connected to the upper portion of the blade housing or the lower portion of the blade housing, and the second end is connected to a support or to a flat back, thereby preventing peeling stress caused by deformation of the adhesive bonding line portion.

2. The wind turbine blade with a total length exceeding 40 meters according to claim 1, wherein, The at least one elongated reinforcing member includes a plurality of elongated reinforcing members positioned at intervals along the longitudinal extension of the blade.

3. The wind turbine blade with a total length exceeding 40 meters according to claim 1 or 2, wherein, At least one of the at least one elongated reinforcing members extends in a direction forming an angle with the longitudinal extension of the blade: the angle is in the range of 70° to 110°, preferably in the range of 80° to 100°, and more preferably in the range of 85° to 95°.

4. The wind turbine blade with a total length exceeding 40 meters according to claim 3, wherein, At least one of the at least one elongated reinforcing members extends in a direction substantially perpendicular to the longitudinal extension of the blade.

5. A wind turbine blade with a total length exceeding 40 meters according to any one of the preceding claims, wherein, At least one of the at least one elongated reinforcing members forms an angle between 10 degrees and 80 degrees with the profile chord of the blade. Preferably, at least one of the at least one elongated reinforcing members forms an angle between 30 degrees and 60 degrees with the profile chord of the blade. Most preferably, at least one of the at least one elongated reinforcing members forms an angle between 40 degrees and 50 degrees with the profile chord of the blade.

6. A wind turbine blade with a total length exceeding 40 meters according to any one of the preceding claims, wherein, The at least one elongated reinforcing member includes a plurality of elongated reinforcing members positioned along the longitudinal extension of the blade at intervals of less than 2×D, wherein D is the distance between the first end and the second end of one of the elongated reinforcing members.

7. A wind turbine blade with a total length exceeding 40 meters according to any one of the preceding claims, wherein, One of the at least one elongated reinforcing members forms an angle with the other of the at least one elongated reinforcing members.

8. The wind turbine blade with a total length exceeding 40 meters according to claim 7, wherein, The angle is in the range of 10° to 50°.

9. A wind turbine blade with a total length exceeding 40 meters according to any one of the preceding claims, wherein, At least one of the at least one elongated reinforcing members is a flexible wire with high tensile strength but lacking the ability to resist compressive forces.

10. A wind turbine blade with a total length exceeding 40 meters according to any one of the preceding claims, wherein, At least one of the at least one elongated reinforcing members comprises a composite material, for example, at least one of the at least one elongated reinforcing members comprises glass fiber reinforced plastic, or carbon fiber reinforced plastic, or any other fiber reinforced material.

11. A wind turbine blade with a total length exceeding 40 meters according to any one of the preceding claims, wherein, At least one of the at least one elongated reinforcing members is connected to the blade housing, or to the support member, or to the flat back.

12. A wind turbine blade with a total length exceeding 40 meters according to any one of the preceding claims, wherein, At least one of the at least one elongated reinforcing members is threaded into the blade housing or threaded into the support member, or screwed into the flat back.

13. A wind turbine blade with a total length exceeding 40 meters according to any one of the preceding claims, wherein, At least one of the at least one elongated reinforcing members is laminated to the blade shell, or to the support member, or to the flat back.

14. A wind turbine blade with a total length exceeding 40 meters according to any one of the preceding claims, wherein, At least one of the at least one elongated reinforcing members is positioned at the inner third, middle third, or outer third of the blade along its length.

15. A method for increasing the strength of a wind turbine blade with a total length exceeding 40 meters, the wind turbine blade having a blade shell with an aerodynamic profile, the method comprising the steps of: At least one elongated reinforcing member is positioned within the blade, wherein each of the at least one elongated reinforcing member has a first end and a second end and extends longitudinally between the first end and the second end; and the first end is connected to the upper portion of the blade housing or the lower portion of the blade housing, and the second end is connected to the support or the flat back, thereby preventing peeling stress caused by deformation of the adhesive bonding line portion.

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